Modification of wool with beta-propiolactone



Patented Aug. i9 :11.

MODIFICATION OF WOOL WITH BETA-PROPIOLACTONE Harrison W. Jones and Harold P. Lundgren,

Berkeley, Calif assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application March 23, 1950, Serial No. 151.556

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 7 Claims.

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented in any country, may be manufactured and used by or for the Government of the United States of America. for governmental purposes throughout the world without the payment to us of any royalty thereon.

This application is a continuation-in-part of our copending application Serial No. 113,895, filed Sept. 2, 1949, now abandoned.

This invention relates to the chemical modification of wool, particularly by reaction thereof with beta-propiolactone under substantially anhydrous conditions.

It has been found that beta-propiolactone reacts with wool under substantially anhydrous conditions to form a chemically modified wool the properties of which are substantially difierent from the untreated wool. Thus the treated wool is softer and whiter; it also acquires a sheen and loses some of its natural kinkiness. Further, the felting property of the treated wool is improved over that of the natural wool; that is, felts prepared from the treated wool have a greater tensile strength than felts produced from the natural wool. Further, the treated wool forms a felt more rapidly than does the natural wool.

The chemical modification of wool in accordance with this invention involves, essentially, contacting the wool with beta-propiolactone so that it can react with this reagent. The proportion of beta-propiolactone to wool can be varied over a wide range depending on the degree of modification desired. For best results the proportion of reactants should be at least 0.3 part of beta-propiolactone per part of wool. Generally. a greater proportion of beta-propiolactoneis used to ensure complete reaction. The unreacted portion ofthe lactone can easily be separated from the reaction mixture and re-used. It is convenient to use such an excess of the lactone that the wool can be immersed in it while the reaction is allowed to take place. In most cases it is convenient to employ the beta-propiolactone in solution form. Any inert organic solvent for the beta-propiolactone can be used, for example, ether, chloroform, carbon tetrachloride, benzene, and so forth. Inany case the solvent should 2 lactone. It has also been found that the wool can be reacted with beta-propiolactone in the vapor phase. In applying this modification of our process, the wool may be placed in a suitable vessel where it is subjected to vapors of betapropiolactone. Since the lactone has a highboiling point (Si-52 C. at 11 mm. Hg), the concentration of the lactone in the atmosphere of the vessel is preferably increased by the use of low-pressures, by applying heat, or by a combination of both. The lactone may also be applied to the wool by passing warm air or other inert gas through a pool of beta-propiolactone and then contacting the lactone-containing gas stream with the sample of wool under treatment. In such type of treatment, instead of an air stream, one can use a stream of carbon tetrachloride or chloroform vapors or the vapors of any other suitable inert solvent which has a low :boiling point. say, C. or less. Usually, as a. matter of convenience, the reaction is conducted at room temperature. However, the temperature may be varied from about 0 C. to about 100 C.. the rate of the reaction increasing as the temperature is increased. In most cases, it is preferred to use a temperature below 40 C. to avoid too rapid reaction which tends to make the product somewhat brittle. The time of reaction will, of course, depend on many factors such as the type of wool, the concentration of betapropiolactone, the temperature, and the type of product desired. In general, it is preferred that the reaction be allowed to continue until the total nitrogen content of the wool is reduced to about 12%. Such a product has especially enhanced felting properties.

Since the reagent, beta-propiolactone, reacts with water to form beta-hydroxypropionic acid. the wool should be dried before the reaction is initiated. Any of the usual drying methods may be used, for example, subjection of the wool to a current of hot (about 100 C.) air. However, to obtain thorough removal of water it is preferred to wash the wool with an organic solvent to displace water from the fibers. For this purpose it is preferred to wash the wool successively with absolute alcohol, dry benzene, and dry ether. However, such vigorous washing is not necessary in all cases.

besubstantially dryto minimize hydrolysis of the 0 After the reaction of the wool and the betapropiolactone has been carried out, the chemically modified wool-is mechanically treated as by wringing, centrifuging or the like to remove excess reagent. Any residual beta-propiolactone is then removed by washing with an inert solvent, as, for example, ether, carbon tetrachloride, chloroform, benzene, and so forth. In many cases it is advisable to also wash the modified wool with an aqueous solution of a weak or moderately alkaline material to remove any beta-hydroxypropionic acid which may have been formed by hydrolysis of beta-propiolactone. As the alkaline material, sodium bicarbonate is preferred although one may use similar materials such as potassium bicarbonate, ammonium hydroxyde, sodium carbonate, potassium carbonate, and so forth. If an alkaline wash is used, it is preferable to then wash excess alkaline material from the wool with water.

With regard to the'chemical reactions which take place in carrying out the process of this invention, it has been determined that the wool actually combines with the beta-proplolactone without destroying the polypeptide chain which makes up the wool molecule. The beta-propiolactone attaches to various groups present in the wool molecule such as amino, hydroxyl, phenol, and carboxyl groups without breaking the polypeptide chain. The following equations illustrate the mechanism of the reaction:

CH(CHi)4NH, CHzCHzCO CH(CH:)NHCOGH2CH1OH Lysine residue \CHCHIOH CHgCHgCO 0 CHCHz-OCHsCHaCOOH Serine residue NH CHCHr-OOH crncmco c6 LO cncrn-oomcmcoon 46 Tyrosine residue CHCHzCOOH CEhCHsCO -NH O \CHCHJEOCHICHQCOOH Aspartic acid residue It is evident from these equations that the beta-propiolactone attaches to various radicals such as amino, imino, hydroxyl, and carboxyl without-altering the chain structure of the basic molecule.

The reaction of beta-propiolactone with wool does not alter the physical form of the wool fibers except to increase somewhat the diameter of the fibers. Thus in general it has been observed that 4 when sufficient beta-propiolactone has reacted EXAMPLEI A 10 gram sample of New Zealand merino wool was dried by washing it successively with absolute alcohol, dry benzene, and anhydrous ether. The wool was then immersed in 500 ml. of a 20% solution of beta-propiolactone in ether. The wool was allowed to remain in the solution for 24 hours. After this period of time the wool was removed from the solution, squeezed to remove excess solution then washed successively with ether, dilute aqueous (about 0.5M) sodium bicarbonate solution, and water. The sample was then dried in warm air.

It was observed that the product was softer and whiter than the original wool; further, it had acquired a sheen and was less kinky than the original material.

A sample of the product and a sample of the original wool were made into felt pads by a standard procedure of carding and padding. The felt pads were tested for tensile strength and it was found that the felt prepared from the betapropiolactone treated wool had a tensile strength twice that of the felt pad produced from the untreated wool.

EXAMPLE II A sample of New Zealand merino wool was dried and reacted with beta-propiolactone as set forth in Example I, the only diiierence being that in this case, the wool was allowed to stand in 0 strength of 2.3 times that of a felt pad produced from the untreated wool.

EXAMPLE III A 10-gram sample of New Zealand merino wool was dried and immersed in 50 ml. of beta-propiolactone and allowed to remain in the liquid at room temperature (20 C.) for 2 days. The chemically modified wool was then removed and squeezed to remove excess liquid then washed successively with ether, dilute aqueous sodium 70 lactone using bicarbonate solution, and water. The sample was then dried in warm air. Analysis indicated that the chemically-modified wool had a total nitrogen content (Kjeldahl method) of 11.1

EXAMPLEIV A batch of New Zealand merino wool was divided into IO-gram samples and each sample was reacted with 250 ml. of a solution of beta-propiovarious solvents, concentrations, and conditions as set forth hereinafter. After the reaction with the beta-propiolactone was completed, the samples of chemically-modified wool were treated to remove excess liquid. washed.

7s anddriedsssetforthinitxamplel. Thevarious conditions used and the results obtained are set forth in the following table:

4. A process in accordance with claim 1 wherein the beta-propiolactone is in the vapor phase.

Table 1 T Total nibigo Amino ntigrgat sass that taste Expt. Reaction liquid reaction (Kieldahl (Van Slyke N 0. method) method) Days 0. Per cent Per cent none used (control) 16.8 0.29 solution of bets-propiolactone in ether 1 4 l5. 7 0. l7 (1.. a 4 15.4 0.22 do 1 20 16.4 0.26 m. 1 20 16.5 0.23 do 1 20 15.5 0.20 7 dn 2 20 14.6 0.18 8... do 3 20 11.6 0.08 9 20% solution of heta-propiolactone in ether 3 20 11. 7 0. 13 10.. 20% solution of bets-propiolsctone in ether 7 20 7. 2 0. 07 ll 20% solution of beta-propiolactone in chloroform. l 40 10. 7 0. 07

In experiments Nos. 2, 3, 6, '7, 8, 9, 10, and 11, 20 5. A process for chemically modifying wool the wool was dried before carrying out the recomprising reacting wool with beta-propiolacaction by washing it successively with absolute tone under substantially anhydrous conditions at alcohol, dry benzene, and dry ether. In experia temperature from about 0 C. to 100 C. for a ment No. 4, the wool was given no drying treatperiod of about from 1 to 3 days, said beta-proment. In experiment No. 5, the wool was first pi01actone being employed inthe proportion of at dried by placing it in an oven at 110 C. for 1 day. least 0.3 part per part of the wool.

6. A process for chemically modifying wool P E V-VAP R PHASE TREATMENT comprising reacting wool, under substantially anhydrous conditions, with beta-propiolactone dis- A 1.5-gram sample of scoured W001 was timed solved in an inert organic solvent at a tempera- 24 hours under Vacuum at 55 ture of about 20 C. until the nitrogen content of The wool was then placed on a watch gla the wool has been reduced to about 12%, said enclosed in a large glass jar. A beakercontaming betammmolactone being emplayed m propor beta-propiolactone was also placed in the 1 tion of at least 0.3 part per part of the wool. The jar was then sealed and the vent in the lid A chemically modified wool which consists connects? to a vacuum Pump to Qxhaust the of the original polypeptide chain which makes up m the and to Obtain maxlmum j the wool molecule and in which the free hydroxyl centration of the lactone in the atmosphere withgroups are etherified by the OCH2CHJCOOH in the jar. The pressure in the jar was reduced group, in which the free amino and immo groups to approximately 8 mm. of Hg and maintained at 40 are idifi d by the around this value for seven days, the jar being 0 maintained at room temperature (20-25 0.). a After this period of time. the treated wool sample CH7CH2OH was removed, washed and dried. The chemicallygroup and m which t free carboxyl groups are modified wool had a nitrogen content of 14.03% ester-med by the ....QCH2CH2CQOH group, and a sample of felt prepared therefrom had a HARRISON w JONES tensile strength twice that of felt produced from HAROLD p LUNDGREN the original, untreated wool felted under identical conditions. REFERENCES CITED iP described the invention what is The following references are of record in the c Mme file of this patent:

1. A process for chemically modifiying wool comprising reacting wool with beta-propiolactone UNITED STATES PATENTS under substantially anhydrous conditions. Number Name Date 2. Aprocess in accordance with claim 1 wherein 1,685,168 Martin Sept. 25, 1928 the beta-propiolactone is in the liquid phase.

3. A process in accordance with claim 1 wherein FOREIGN PATENTS the beta-propiolactone is dissolved in an inert Number C n y Date organic solvent, 249,942 Germany Aug. 2, 1912 14,675 Australia Oct. 10, 1933 

1. A PROCESS FOR CHEMICALLY MODIFYING WOOL COMPRISING REACTING WOOL WITH BETA-PROPIOLACTONE UNER SUBSTANTIALLY ANHYDROUS CONDITIONS. 